1. Field of the Invention
The present invention relates to an image pickup apparatus using an eye point detection function of detecting an eye point of an operator in a frame.
2. Related Background Art
Conventionally, in the field of cameras, automated functions and multi-functions are used more often, and especially, a video camera has various functions such as an automatic exposure device, an automatic focus adjustment device, and the like as standard functions.
In particular, since an apparatus such as a video camera for picking up a dynamic image must keep focusing on an object which changes constantly, an automatic focus adjustment device is indispensable. However, the automatic focus adjustment device may often cause an erroneous operation, e.g., may be unfocused or may focus on an object other than an object of interest depending on an image pickup condition.
Thus, an automatic focus adjustment device using an eye point detector for detecting an eye point position of a user in a frame, setting a distance measurement frame at the coordinates of the eye point, and performing a focusing operation on the basis of a focus signal in the distance measurement frame has been proposed. However, when the eye point position changes too fast, and the position to be focused changes frequently, an unstable image which changes frequently is obtained, and the picked-up image may be degraded. When the size of the distance measurement frame is fixed, the eye point position cannot often be precisely focused. In this manner, various problems remain unsolved, and it is difficult to realize such a device. Note that U.S. Pat. Nos. 4,075,657, 4,109,145, 4,574,314, and the like are known as the patents associated with the eye point detector.
As for the automatic focus adjustment device, in particular, in the field of video cameras, the following technique is popular. That is, a signal corresponding to the amount of sharpness of an object image is extracted from a video signal output from, e.g., an image pickup element, and the position of a focusing lens is controlled to maximize the amount of sharpness, thereby focusing on the object.
The amount of sharpness is increased as the value of a high-frequency component in an image pickup frame is increased, and is detected on the basis of the magnitude of a high-frequency component of a video signal extracted by a band-pass filter, a blurred width magnitude (an evaluation value according to the reciprocal number of the width of an edge) of an edge portion extracted by a differential circuit, or the like. As for the blurred width detection magnitude upon a pickup operation of a normal object image, since the edge width of an object image is wide in an unfocusing state, the evaluation value is low. As the focusing lens approaches the focusing state, the edge width is decreased, and the evaluation value is increased. In the focusing state, since the edge width is minimized, the evaluation value is maximized.
By utilizing this nature, the focusing lens is driven as quickly as possible in a direction to increase the amount of sharpness. As the amount of sharpness is increased, the focusing lens is driven slowly, and is stopped with high precision at the top of the hill, thereby focusing on an object (such an automatic focus adjustment (AF) method is called a hill-climbing AF method).
However, in the above-mentioned example, since the speed of the focusing lens group is set according to the high-frequency component value by the hill-climbing AF method, the amount of sharpness and the dynamic range for an object vary considerably, and wrong driving control, focusing judgment, or reactivation judgment upon controlling of the focusing lens group may be made. As a result, the focusing lens group is stopped in an unfocusing state, or cannot be stopped at a focal point with high precision, thus causing so-called hunting.